Micro-scale analysis of mesenchymal to epithelial transition in lung cancer. The mesenchymal to epithelial transition (MET) is the counterpart to the epithelial to mesenchymal transition (EMT). During embryogenesis, this bidirectional change of cell state allows differentiated epithelial cells to take on stem-like mesenchymal properties (EMT), detach from their basement membrane, migrate, attach and form new epithelial structures (MET). The EMT process has been shown to be generalizable and involved in many aspects of organogenesis. Although MET is equally important, there is currently little direct experimental evidence. The inherent plasticity of epithelial cells to undergo a mesenchymal transition explains several key features of the invasive and metastatic phenotypes in epithelial cancers. By activating this pathway, epithelial cells in the early phases of neoplastic transformation could detach, gain motility and change their transcriptome in ways that favor invasion. Upon reaching a hospitable niche, such neoplastic cells could revert, wholly or in part, to an epithelial state through MET. The present proposal will use a novel methodology integrating flow cytometric cell sorting, microprinting, microculture and microscopic imaging to directly demonstrate MET for the first time in unpassaged samples from non-small cell lung cancer patients. This technology will allow complex experiments to be performed using cells from primary samples where cells of interest are rare, or the sample itself is limiting. In the firt Aim, we propose to identify cytokines and other factors capable of driving MET using sort-purified unpassaged non-small cell lung cancer cell subsets in an in vitro microculture system. The second Aim will address the potential effects of sort-purified vascular endothelial cells, pericytes and mesenchymal stromal cells on MET.